1. Field of the Invention
The invention relates in general to meter apparatus for measuring and totalizing electrical energy usage, and more specifically to multiple rate metering apparatus.
2. Description of the Prior Art
Multiple rate meters have been used in the prior art to enable an electric utility company to charge a customer different rates, based upon predetermined parameters, such as the amount of electrical energy used while the load is below a predetermined K.W. level, and the amount used while the load is at or above this K.W. level. For example, U.S. Pat. No. 1,142,425 discloses a meter having two registers, one which records the energy to be billed at a first rate, and one which records the energy to be billed at a higher rate. A spring on a relay is adjustably tensioned to cause the relay to operate at a selected load and cause a gear member engaged with the driving worm of a rotatable meter shaft to engage the gear of the desired register.
U.S. Pat. No. 1,957,010 discloses a meter having a single register with one of two gears being selected remotely when a tariff change is desired. The two gears drive the register at different speeds for a predetermined input speed.
U.S. Pat. No. 2,037,447 discloses a meter having two registers, with bimetal strips or springs, which are heated by load current, or a current proportional to load current, being operative to shift the worm gear on the meter disc shaft from driving one register to driving the other register.
U.S. Pat. No. 2,130,201 discloses a meter having first and second registers, which shifts from the first register to the second register after a predetermined amount of electrical energy is recorded on the first register during a predetermined time interval. The energy used during the remaining portion of the time interval is recorded on the second register.
Still other multiple rate meters register total K.W. hour usage on one register, and K.W. hour usage above an established demand level on a second register. One such system employs a synchronous motor driving differential gearing in an arrangement which totals K.W. hour usage on the second register when the differential is driven by the meter at a speed above the chosen K.W. level.
The multiple rate meters of the prior art which switch registers, or change the driving speed of a single register through a gear change, or which record total K.W. hour usage on one register and selectively activate a second register responsive to the level of power usage, all have one or more of the following disadvantages. They are mechanically complex and require periodic maintenance to insure dependable, accurate switching at the desired K.W. level, and/or the demand level at which the desired switching action occurs is difficult to change by the electrical utility user, i.e., it may be set by the original gearing, as in the case of the differential gearing apparatus hereinbefore described.
It would be desirable to provide a new and improved multiple rate meter which is mechanically simple, requiring little or no maintenance, which may be easily set to the desired K.W. level, and just as easily changed to a different K.W. demand level by the electrical utility, if desired.